The Tennessean Editorial Board noted the senator's courage and independence and fight to end human slavery.

WASHINGTON — Reports that Sen. Bob Corker may be rethinking his decision to retire and that he might seek re-election have upended one of Tennessee’s hottest political contests, injecting uncertainty and charges of sexism into the GOP primary.

Rep. Marsha Blackburn, considered the front-runner in the GOP primary to succeed Corker, pushed back hard Tuesday against reports that some establishment Republicans are trying to get Corker to re-enter the race because they worry the party could lose reliably red Tennessee to Democrat Phil Bredesen in November.

Sen. Bob Corker announced in September that he would not seek re-election. According to reports, ...more

Sen. Bob Corker announced in September that he would not seek re-election. According to reports, some Republicans are encouraging him to run again. His spokeswoman said Tuesday that Corker "has been encouraged to reconsider his decision and is listening closely.”

Jack Gruber / USA Today

“Anyone who thinks Marsha Blackburn can’t win a general election is just a plain sexist pig," Blackburn spokeswoman Andrea Bozek said in an emailed statement to the USA TODAY NETWORK – Tennessee.

"She’s the best fundraiser in the country and is beating Phil Bredesen in several polls. We aren’t worried about these ego-driven, tired old men in Washington. Marsha has spent her whole life fighting people who told her she wasn’t good enough and she will do it again.”

The statement was striking not only for its tone but also because Blackburn in the past has talked about the need for more civility and less name-calling in politics.

“I agree with so many moms — the pettiness, the infighting, the name-calling, the focus on negative advertising. What we need to do is just stop it and shift that focus to talking about what we are for," she said during a 2012 interview.

One source of the GOP angst is a new poll conducted by Glen Bolger of Public Opinion Strategies, a prominent Republican pollster, that shows Bredesen, a moderate Democrat and former two-term governor, beating Blackburn 47 percent to 45 percent. That means the race is statistically a dead heat.

Rep. Marsha Blackburn is considered the front-runner in the GOP primary to succeed Sen. Bob Corker.

Rep. Marsha Blackburn is considered the front-runner in the GOP primary to succeed Sen. Bob Corker.

George Walker IV / File / Tennessean.com

More troublesome for Blackburn, the same poll, which was obtained by the USA TODAY NETWORK – Tennessee, asked voters whether they would back a generic Republican or a generic Democrat in a congressional race this year. The generic Republican was favored by a 10-point margin.

For his part, Bredesen said Tuesday he’s running regardless of whether Corker gets back into the race.

The Corker speculation "changes nothing," Bredesen spokeswoman Alyssa Hansen said. Bredesen entered the race in December, just three months after Corker’s announcement that he planned to retire when his current term is up.

"Governor Bredesen got in this race to be a true advocate for the people of Tennessee in the Senate, not to run against anyone," Hansen said in a statement. "As he travels to all corners of the state, the governor's case for bringing Congress back to basics is clearly resonating with Tennessee voters."

Corker, who chairs the Senate Foreign Relations Committee, announced in September that he would not seek re-election, saying he felt like the time had come for him to leave the Senate after serving two terms. Afterward, he returned $1.2 million in campaign donations.

On Sunday, CNN reported that some Republicans were encouraging him to run again, and a senior adviser to the senator confirmed that he is being urged to reconsider.

“In recent days, people across Tennessee have reached out to Senator Corker with concerns about the outcome of this election because they believe it could determine control of the Senate and the future of our agenda,” she said. “The senator has been encouraged to reconsider his decision and is listening closely.”

If Corker does re-enter the race, the result could be an ugly primary, said Jennifer Duffy, who tracks Senate races for the nonpartisan Cook Political Report in Washington.

“I cannot imagine that Marsha Blackburn will back down,” Duffy said, citing the campaign’s charges of sexism as a sign that Blackburn intends to play hardball.

Duffy lists the Tennessee contest as a “toss-up” in November, which means it’s a possible pickup for Democrats as they look to retake the Senate majority.

Corker would be a strong contender in November, Duffy said, but first he would have to explain to voters why he changed his mind.

He would not be the first senator to announce his retirement and then backtrack. Sen. Marco Rubio, R-Fla., decided to run for president in 2016 instead of seeking another Senate term, but changed his mind after losing in the presidential primary. He went on to win a second term later that year.

Corker’s situation is different, Duffy said.

“Rubio decided not to run because he was running for president,” Duffy said. “Corker basically said he’d had enough. So what is his justification going to be for why he wants to run again?”

Victor Ashe, a Republican and a former Knoxville mayor, predicted Corker would have an uphill climb if he decides to get back in the race.

“For him to be successful, I think President Trump would probably have to endorse him and come to Tennessee,” said Ashe, who served as U.S. ambassador to Poland under Presidents George W. Bush and Barack Obama.

But whether Trump would be willing to back Corker, much less campaign for him, is far from certain since the senator and the president spent much of last year in a public, sometimes nasty feud. At one point, Trump mocked the senator as “Liddle” Bob Corker and argued he couldn’t get elected dog catcher.

Blackburn, on the other hand, has been a loyal Trump soldier. She served as a Trump surrogate during the presidential campaign and was a member of the team that assisted in his transition from candidate to president.

The White House did not respond Tuesday to questions about whether Trump would weigh in on the Senate race. But the feud between Corker and Trump has shown some signs of thawing. Corker has spoken favorably of Trump recently and accompanied him aboard Air Force One when Trump traveled to Nashville to give a speech last month.

On Monday, the day after the CNN story that Corker was having second thoughts about retirement, the senator went to the White House for a meeting with the president’s daughter, Ivanka Trump, although it was not immediately clear whether the campaign was discussed.

Meanwhile, speaking to reporters in Nashville on Tuesday, Republican Gov. Bill Haslam said he has not encouraged Corker to potentially seek re-election. Given Tennessee’s political leanings, the chances of a Republican winning the Senate seat or the governor’s race are strong, Haslam said, but there are challenges for GOP candidates seeking both offices.

“This is a midterm election and any party in the White House … they tend to lose seats in state races,” Haslam said, adding the Democrats have a strong candidate in Bredesen.

Ashe, who has donated to the campaign of another Republican in the race, former Rep. Stephen Fincher, declined to say whether he would support Blackburn if she finds herself up against Bredesen in November.

“I know Bredesen well and thought he did a good job as governor, but running for U.S. Senate as a Democrat is different than running for governor,” Ashe said. “But I will certainly say he’s a Tennessee Democrat and not a national Democrat. Tennessee Democrats are different from national Democrats. They are not as liberal.”

Mary Mancini, chairwoman of the Tennessee Democratic Party, said it doesn’t matter whether the Republican candidate is Blackburn or Corker.

“Both have put their political party and ambitions ahead of the people of Tennessee,” she said. “… Whoever the Republican nominee is, Tennesseans already have the best choice in Governor Bredesen. Bredesen will work on solving the everyday problems that Tennessee families face instead of getting the same from Blackburn and Corker, disengaged career politicians who have done nothing but harm the people of Tennessee.”

Reporters Joel Ebert in Nashville and Eliza Collins of USA Today contributed to this story.